Why doesn't my cat like to be pet?

I have two cats, one being older than the other, but they are both related (same mom). My older cat loves to be pet to an extent, but the younger one will not let you pet her. She will come up to you and act like she wants you to pet her, but when you touch her, she runs away. Could there be any reason for that?

Status

Cast your vote for which answer you think is best!

Answers

Some cats, like some people, absolutely HATE to be touched. Some will let you pet them, then turn on you, claws out, and attack you for no apparent reason. As long as you're sure that no one teases the younger one, chases her, tries to pick her up or otherwise harrasses her, this is just her personality and she should not be forced to tolerate unwanted attention. She may change as she grows up. Delilah was a biter and after I had her for about 4 years, she's now a loving lapcat.